There is a number of ready to use “shields” – add-on boards – for the WeMos
D1 Mini, containing useful components together with all the necessary
connections and possible additional components. All you have to do is plug such
a “shield” on top or bottom of the WeMos D1 Mini board, and load the right code
to use the components on it.

It is recommended to use this shield with the “dual base”, so that the
temperature sensor is not right above or below the ESP8266 module, which tends
to become warm during work and can affect temperature measurements.

That shield has a single addressable RGB LED on it, connected to pin gpio4.
Unfortunately, that means that this shield conflicts with any other shield that
uses the I²C protocol, such as the OLED shield or the motor shield. You can use
it with code lik this:

This shield contains a relay switch, together with a transistor and a couple of
other components required to reliably connect it to the board. It uses pin
gpio5, which unfortunately makes it incompatible with any other shields
using the I²C protocol, such as the OLED shield or the motor shield. You can
control the relay with the following code:

A small, 64×48 monochrome display. It uses pins gpio4 and gpio5 to talk
with the board with the I²C protocol. It will conflict with any other shield
that uses those pins, but doesn’t use I²C, like the neopixel shield or the
relay shield. It can coexist with other shields that use I²C, like the motor
shield.

Up to two such displays can be connected at the same time, provided they have
different addresses set using the jumper on the back.

The motor shield contains a H-bridge) and a PWM chip, and it’s able to drive up
to two small DC motors. You can control it using I²C on pins gpio4 and
gpio5. It will conflict with any shields that use those pins but don’t use
I²C, such as the relay shield and the neopixel shield. It will work well
together with other shields using I²C.

Up to four such shields can be connected at the same time, provided they have
different addresses selected using the jumpers at their backs.

This shield lets you connect a micro SD card to your board. It connects to pins
gpio12, gpio13, gpio14 and gpio15 and uses SPI protocol. It can
be used together with other devices using the SPI protocol, as long as they
don’t use pin gpio15 as CS.

You can mount an SD card in place of the internal filesystem using the
following code: